1. Field of the Invention
This invention relates to containers, and more particularly to self-locking containers which, once closed, cannot be opened without giving a visual indication of that fact.
Containers of the type here contemplated find a wide variety of applications. For example, in many jurisdictions, apartment dwellers or lessees are required to provide the landlord a key to their premises. These keys are often stored in readily available locations and tagged to identify the premises to which they provide access. Many tenants are uncomfortable with this requirement since they cannot know when or for what reason their premises have been entered, unless specifically advised. Thus, there is a need for a key storage system which will enable a tenant to know that access has been had to his key, and thus his premises; and, at the same time to store the key in a manner which will limit identification of the premises to which the key provides access.
2. Description of the Prior Art
A number of self-locking cartons or the like are known which are fabricated at least partially from cardboard or paperboard, as disclosed, for example, in U.S. Pat. Nos. 2,834,531 and 3,025,958. Containers of this type may be opened by cutting with a sharp, thin blade along a crease or corner and then reclosing them with a transparent adhesive or the like to prevent or delay detection of tampering.
Other containers employ a tear sheet to expose adhesive surfaces, as taught in U.S. Pat. No. 3,144,935 to gain access to the container contents, such containers being resealable, while U.S. Pat. No. 3,896,965 is directed to a tamper indicator tape for a hermetically sealed container, the tape being removable and changing color when flexed to indicate that the container has been tampered with. U.S. Pat. No. 4,197,940 discloses a transparent container cover which becomes opaque when flexed.
Additional patents of interest are U.S. Pat. Nos. 655,894, 2,734,624, 3,367,488, 3,527,400, 3,835,995, 3,924,746 and 3,949,931.